1. Field of the Invention
The present invention relates to a method of forming a wiring film in a semiconductor production process. In particular, the present invention relates to a method of forming a wiring film that can be patterned into low resistance wiring for semiconductor circuits having ultra-large-scale-integration (xe2x80x9cULSIxe2x80x9d).
2. Description of Related Art
The degree of integration in semiconductor circuits has increased rapidly in recent years. Future increases in operational speeds appear to be limited by the dielectric constant of the SiO2 used in insulation films in the circuits and by the electrical resistance of Al wiring typically used in ULSI circuits. A demand has developed for insulation films made of materials with lower dielectric constants than SiO2 and for wiring with lower electrical resistance than Al.
Metals with lower electrical resistivity than aluminum, such as copper, copper alloys, silver and silver alloys, have been studied in attempts to lower the electric resistance of conventional Al wiring.
Copper materials are considered to be the most promising replacements for aluminum, because copper materials have low electrical resistance, exhibit minimal electro-migration, and are available at a reduced cost.
Because it is difficult to form wiring structures by etching copper or silver materials sputtered onto conventional insulation films, wiring structures are often formed by electroplating material into trenches formed in insulation films. Electroplating can be used with organic insulation films. However, organic insulation films often exhibit poor heat resistance.
The electroplating method, referred to as a low temperature process, requires annealing at 300 to 400xc2x0 C. to stabilize electroplated wiring before actual use. When a copper film is plated, the size of crystal grains in the film tends to increase even when the copper film is left at room temperature. Plating solution can be confined between crystal grains. As a result, voids are formed during the crystal grain growth. Although plated copper films are typically heated to about 300 to 400xc2x0 C., the voids cannot be completely eliminated. Electrolytic plating methods are often adopted in order to control the rate of film formation. However, electrolytic plating requires that a seed layer be provided on the surface of a semiconductor wafer by a sputtering process or a CVD process to make the surface electrically conducting. In contrast to conventional processes for forming Al wiring, enormnous equipment installation costs are associated with plating methods. In addition, plating methods incur relatively high costs associated with disposal of plating liquid wastes.
To overcome the problem of the poor heat resistance of organic insulation films, a method has been proposed in which copper or silver films are first sputtered at low temperatures and then heat treated in hydrogen or a mixed atmosphere of hydrogen and oxygen (redox). Hole diameters in integrated circuits are expected to decrease from 0.25 xcexcm at present to about 0.1 xcexcm by the year 2003. Sputtering and plating methods have difficulty filling holes and trenches of these dimensions, particularly when holes have diameters of 0.15 xcexcm or less and depths of four or more times the diameter. To fill holes and trenches at these reduced dimensions, the present inventors have proposed a method of first closing the openings of the holes or trenches with a metal film and then annealing the metal film at high temperatures in a highly pressurized gas (high pressure annealing method).
However, in the case of a copper wiring film formed by a sputtering process, a high temperature at 450 to 500xc2x0 C. is necessary even when the pressure in the high pressure annealing method is increased, for example, to 200 MPa. On the other hand, as discussed above organic insulation films often lacks heat resistance. For all organic insulation films, the heat treatment temperature must be 400xc2x0 C. or less, particularly, for fluorocarbons and benzocyclobutene, which have been noted as interlayer insulation films. As a result of the poor heat resistance of organic insulation films, the high pressure annealing treatment cannot be practiced with copper wiring films.
To overcome the foregoing problems in the prior art, the present inventors have made an earnest study and, as a result, have accomplished the present invention outlined as described below.
The present invention provides a method of forming a wiring film that can be patterned into wiring for semiconductor circuits.
In a first aspect of the invention, the method comprises providing holes or trenches in an insulation film on a substrate; covering the surface of the insulation film with a metallic material such as copper, copper alloy, silver or silver alloy under an atmosphere containing hydrogen; and then applying a high temperature/high pressure treatment to the metallic material to fill the metallic material, preferably completely, into the holes or trenches.
In a second aspect of the invention, the method comprises providing holes or trenches in an insulation film on a substrate; covering the surface of the insulation film with a metallic material such as copper, copper alloy, silver or silver alloy; then applying an annealing treatment to the metallic material in an atmosphere containing hydrogen and oxygen or in an atmosphere containing steam; and then applying a high temperature/high pressure treatment to the metallic material to fill the metallic material, preferably completely, into the holes or trenches.
In a third aspect of the invention, the method comprises providing holes or trenches in an insulation film on a substrate; covering the surface of the insulation film with a metallic material such as copper, copper alloy, silver or silver alloy; and then applying a high temperature/high pressure treatment to the metallic material in a mixed atmosphere containing hydrogen, a mixed atmosphere containing hydrogen, or an atmosphere containing steam to fill the metallic material, preferably completely, into the at least one hole.
The wiring film can be formed from metallic material deposited in a sputtering process in an inert gas atmosphere containing a hydrogen gas. The mixing ratio of the hydrogen gas to the inert gas can be from 1/99 to 20/80. The distance between the sputtering target and the substrate can be from 100 to 300 mm. During the sputtering, the substrate can be at a temperature from room temperature to 200xc2x0 C.
The annealing treatment can be performed under an atmosphere containing one or more of hydrogen, oxygen and water (steam).
The high temperature/high pressure treatment can be conducted in an atmosphere comprising an inert gas, preferably more than 50% inert gas. The treatment can also be performed in an atmosphere containing one or more of hydrogen, oxygen and water (steam). The atmosphere can comprise a gas having an oxidative effect on the metallic material and a gas having a reducing effect on the oxide of the metallic material.